Recently, industrialization of aliphatic polycarbonate is proceeding as a method for reducing generation of carbon dioxide, for preparing measures against global warming. Aliphatic polycarbonate which is a rubbery plastic having a soft texture, has excellent processability, and is easily controllable in terms of its degradation property, and thus, has been much researched as a biodegradable polymer. However, since the aliphatic polycarbonate has a low glass transition temperature (Tg), and is easily degradable around 200° C., it is characterized by having weak thermal resistance. Further, it has a low modulus of elasticity as the mechanical physical properties, and a thin film product prepared therefrom has a brittle property, so that it has a limitation in use in various fields. Thus, a technique to raise a glass transition temperature or thermal resistance, or to improve mechanical strength through a blend with various resins, is demanded. For example, U.S. Pat. No. 4,946,884 discloses a resin composition produced by melt-kneading polypropylene carbonate with polymethyl methacrylate (PMMA) or including a binder for molding process of ceramics or metal powder, and U.S. Pat. No. 4,912,149 discloses improvement of a mechanical property by melt-kneading polyvinyl chloride acetate. However, since these inventions have limitation in an improvement of mechanical physical properties only by a blend with a different kind of resin, a structural improvement is needed.